Dust cap for valve stems of pneumatic tires



April 2l, 1925.

F. S. HAMILTON DUST CAP FOR vVALVE STEMS OF PNEUMATIC TIRES` Filed March 27, 1920 30. ment, from the stem, it has been proposed to Patented Apr. 21, 1925.

PATENT OFFICE.

FRANK S. HAMILTON, OF BOSTON, MASSACHUSETTS.

DUST CAP FOR VALVE STEMS OF PNEUMATIC TIRES.

Application led March 27, 1920. Serial No. 369,259.

It has hitherto been proposed to employy caps having interruptedv interior threads whereby, when the cap is positioned upon a stem that is provided withcorresponding interrupted exterior threads, with the threaded'portions of each juxtaposed to the unthreaded portions of the other, the cap may be quickly longitudinally thrust down as far as it` will'go on the stem. vA quarter turn Aof the cap lthen results in the cap threads engaging the stem threads to secure and tighten .the cap upon the stem. The cap may become as easily detached from the stem by a quarter turn in the opposite direction when it is ready to be pulled off. The customary necessity for laboriously screwino` the cap upon and'of the stemlis thus avoided. As a cap of this character should be secured against jarring loose, or accidental displacesupply the cap with a terminal collar that is not rotatable on the stem, and then, by a lost motion device involving the indeterminate slipping of afriction cam clamp, to prevent the unscrewing of the cap. However, it has not heretofore been found possible to lock the cap against accidental displacement `save'by externally applied mechanism.V

An object of theinvention is to provide a cap of the above described character which shall be quickly set and screwed tight, practically with only `two motions, and shall thereby become automatically locked against accidental displacement.

7 f A further .object of the invention is to improve upon valve 4caps, rendering them simpler in construction, more efficient in operation, more durable and cheaper to manufacture.

With the above ends in view the invention consists of the improved valve cap hereinafter described, an embodiment of which is illustrated in the accompanying drawings. It is intended that the patent shall cover, by

f suitable expressiony inthe appended claims,

whatever patentable novelty exists in the invention disclosed.

In the drawings;

Figure 1 is a side elevation in medial section of the cap constructed according to a preferred embodiment of the invention, shown engaged upon a valve stem;

Figure 2 is a perspective view of the terminal collar;

vFigure Sfis an end view in section on the line 3-3 of Fig. 1;

Figure 4 is a side elevation of the cap which is shown in section in Fig. l;

Figure 5 is an end View in section on the line 5-5 of Fig. l;

Figure 6 kis a similar view, showing the cap in position on the stem but disengaged therefrom. f

Figure 7 is an end view, in section on the line 7 7 of Fig. 4; and

Figure 8 is an end view at the open end of the cap. The cap 2 has externally a cylindrical shape, but internally it has major and minor diameters perpendicular to each other, and is provided with internal oppositely positioned, interrupted threads 4 at the ends of the minor diameter, and oppositely positioned unthreaded faces 6 alternately disposed to the interrupted thread faces 4, being at the ends of the major diameter. The cap is adapted to co-operate with a valve` stem 8 of a pneumatic tire valve, such as are used on automobiles, or any similar threaded stem having external oppositely disposed interrupted threads 10 and unthreaded or flat faces 12 alternately disposed with respect to the threaded faces 10. The cap may be put on the stem with its threaded faces juxtaposed to the unthreaded faces of the stem as shown in Fig. 6, and quickly pushed home to the limit shown in Fig. 1, by a sliding movement. A quarter turn of the cap about its axis will cause the threads then to engage, securing the cap upon the stem. Being so engaged, a quarter turn in the opposite direction will effect the disengagement of the threads, permitting the cap to be pulled straight off. The cap is thus adapted for quick detachable' engagement upon the stem.

A collar or sleeve 14 is rotatably mounted upon the open end Vof the cap and is provided with internal flat faces 16 adapted to engage the flat faces 12 of the stem tol Y prevent rotative movement of the sleeve ".pon the stem, though permitting sliding movement thereof longitudinally of the stem. The two are held together by an interiorly projecting member 1S which may be a mere dent in the sleeve, that projects into quarter-circumferential slot 2O in the cap near the open end thereof, whereby any substantial relative longitudinal movement of the cap and the collar is prevented.r and relative rotative movement thereof is limited to about a quarter turn. The sleeve is provided at one end with a circular inward projecting shoulder 22 upon` which the open end of thel cap is seated. At its other end, the sleeve is longitudinally slotted at 24 and 26 at points about 900 apart, making a spring tongue B-l between the slots, and the cap has an exterior projection 28, which may be a mere. outward dent, on its wall at a` point whose travel underlies this tongue when the cap is turned on the stem to engage or disengage it, this projection being adapted; if desired and as shown, to engage the outer walls of the slots to limit therelative rotative movement of the cap and the sleeve', and being adapted to spring the tongue outward .when it moves from either limit toward the other. The parts of the tongue at the inner walls of the slots are bulged outwardly at 30 and 32 to receive the projection 28 and to let the tongue spring back when the projection is at either of its limit-ing positions. Owing to the spring action of the tongue 34 between the slots 24 and 26, the projection 28 acts, in conjunction with the bulged out portions 30 and 32, as a latch to lock the cap and the sleeve against accidental displacement from either of said limiting positions. The slot 2O with theiprojection 18, engaged therein,- therefore, and the walls of the slots 24 and 26 with the projection 2S, both limit relaliv'e'rotation of the cap and the sleeve. The projection 18 and the slot 20, further,- prevent escape' of the sleeve endwise. The tongue Se and the projection 28 constitute a spring latch and lock the parts against accidental relative movement. And the gradual or cam development of the inner sides of the bulges 80, 32, as seen in Figures 2 and 3, makes it possible for the o'perator by hand to turn the cap so as to spring the tongue out to let the bulge 28 pass, such springing being accomplished by the bulge itself u'pon the cap being turned with sufficient force.

In operation, the cap and the collar carried thereby will be quickly assembled to their limiting'- position upon the stem by a sliding longitudinal movement as above described. lThe cap may then be rotated a quarter tur'n to' cause the threads t and 10 to engage. It the threads do vnot thus engage when one tries to turn the cap, the

cap may be removed and repositioned 1530o away when they will engage. Bur'ingr' this quarter turn movement the sleeve lll remains stationary owingto the engagement of 'faces 16 with the faces 12. The quarter turn movement therefore causes the projection 2S to travel from its limiting positionrat the slot 26 to the limiting position at the slot 2e, and there is corresponding movement of the projection 18 in the slot 20. As backward movement ofthe cap with respect to the sleeve is' prevented by the spring tongue 34 which snaps down behind the projection 28; and as rotative movement of the sleeve upon the stem is prevented bythe faces 1G engaging the faces 12, the cap becomes thus locked against accidental displacement. The cap thus becomes automatically locked against rot-ative movement in either direction upon its being actuated to either limit of its movement relative to the sleeve. The slot 20 is wi'delenough to let the sleeve move a little longitudinally relative to the projection 18, during` the quarter turn, threadengaging movement. This may be to a degree substantially equal to one-fourth the pitch of the thread but preferably a triiie less, permitting the threads 4e to bind upon the threads 10,- and the projection 18 to bind upon a wall of the slot 20, and thus' to serve as an additional locking medium against displacement.

According to the present invention, therefore not only is the cap quickly engaged upon the stem, but it becomes automatically locked thereon by the same movement which effects the engagement.

It will be understood that the part herein referred to as the stem is not a. valve stem in the strict sense, but is the so called stem which projects from a pneumatic tire, inward through the rim and contains the tire` valve, encasmg it except the end which it is the function of the cap to close.

l claim as my invention:

1. A covering for a stem having interrupted threads, comprising a. cap having interrupted threads adapted to slide past the interruptions of the stem threads to permit longitudinal movement of the covering and adapted to engage the stem threads to prevent said longitudinal movement, and having a projection; and a sleeve on the cap, movable longitudinally with the cap along the stem but not rotatably about the stem, having a slot whose two walls engage the said projection when the cap has been rotated into engagement with the stem threads, thereby locking the cap against rotation.

2. A covering for a stem having interrupted threads, comprising a cap having interrupted threads adapted to slide past the interruptions of the stem threads to permit longitudinal movement of the covering and adapted to engage the stem threads to preventsaid longitudinal movement, and havingr a projection; and a sleeve on the cap, movable longitudinally with the cap along the stem but not rotatable thereabout, being longitudinally slit at two places, and providing a spring tongue therebetween; the outer Walls of the slits rigidly engaging the projection to limit positively the rotative movement of the cap, and the tongue yieldingly engaging the projection thereby locking the cap yieldingly against rotative movement away from the outer Walls of said slits.

3. A cap adapted to cover a stem having external interrupted threads, said cap having internal interrupted threads adapted to slide over the interruptions of the stem threads, combined with a terminal sleeve slidable longitudinally but non-rotatably upon the stem; said sleeve being permanently secured on said cap by means of a transverse slot in one member and a projection from the other member into this slot, said cap and sleeve being relatively rotatable for the length of the slot.

Signed at Boston, Massachusetts, this 25th day of March, 1920.

FRANK S. HAMILTON. 

